The field of prosthetic implants to treat conditions of fracture, arthritis and other such conditions has grown greatly in the past 2-3 decades, and much work continues in these areas. Pyrocarbon-coated graphite materials have proved to be extremely wear-resistant and biocompatible, and they have become the materials of choice for certain applications where strength and other parameters can be met. U.S. Pat. Nos. 5,645,605, 6,159,247, 6,217,616, and 6,699,292 and Published Patent Application No. 2005/0033426 are examples of prosthetic implants that can be used at biological joints in the human body or the like. Although these patents illustrate the use of integral structures for such implants, there is also interest in constructing bone implants, particularly those having an articular head, with a biocompatible metal alloy stem and a head of brittle crystalline material, such as pyrocarbon-coated graphite. Such a combination is considered to have certain advantages because the properties of pyrocarbon can be tailored to more closely match properties of bone where an interface will occur, generally at an articulating surface. However, the differences between the structural properties of metal alloy stems and pyrocarbon-coated graphite heads pose a problem in designing such implants that can be effectively assembled and will have long lifetime. U.S. Pat. No. 6,997,958 recognizes the problem and proposes to limit the amount of tensile stress that may be applied to a head of brittle material when a Morse taper connection is employed; however, such a solution leaves the brittle head subjected to residual stress throughout its lifetime which may not be desirable. As a result, other solutions to this problem have continued to be sought.